Heat-sealed valve bag



I March 16, 1948. HARTMAN (2,437,693

v HEAT SEALED VALVE BAG Filed Au 7, 1944 2 Sheets-Sheet. 1

gmimw EARL H. HAHTMAN Much m, 1948. H, HAR N 2,437,693

mm SEALED VALVE BAG Filed Aug. 7,1944 2 Sheets-Sheet 2' kg Iii-5 I Y a LI Q1 h i g I "6 I g7 1' L g1 w $49 l l I l 12+ Patented Mar. 16, 1948UNITED STATES PATENT OFFICE HEAT-SEALED VALVE BAG Carl Henry Hartman,New Rochelle, N. Y., as-

signor to St. Regis Paper Company, New York, N. Y., a corporation of NewYork v Application August 7, 1944, Serial No. 548,393

This invention relates to sealing bags so as to make them substantiallywaterand gastight, or to resist chemical, solvent, or other deleteriousaction of the contents. More particularly, it relates to sealing bagscomposed of one or more plies of paper and atleast a partial lining ofthermoplastic material. The invention is especially applicable to bagsclosed by a sewn seam, and may be used readily with valve bags.

In sewed end bags, there has been some difficulty encountered incompletely avoiding leaks through the needle holes of the seam, andthere is always danger of leakage through improperly closed valves ofvalve bags. It is the primary ob- Ject of this invention to eliminate orminimize these difilculties. Other objects and features of the inventionwill appear as the description proceeds.

In the accompanying drawings forming a part of this specification Fig. 1is a side elevation of a valve bag end to which the invention has beenapplied.

Fig. 2 is a section on the line 2--2 of Fig. 1 through the seam.

Fig. 3 is a section on the line 33 of Fig. 1, but showing the valveclosed after the bag has been filled.

Fig. 4 is a view of a sheet adapted toform a sleeve in a valve, and Fig.5 is a view of the sheet shown in Fig. 4after portions thereof have beenfolded.

Fig. 6 is a side elevation of the bag end and of a heat-sealing deviceduring the heat-sealing operation.

Fig. '7 is a section on the line 'l--'i of Fig. 6, and

Fig. 8 is a section on the line 88 of Fig. 6.

In the illustrated embodiment of the invention,

it is applied to a gusseted valve bag.

As illustrated, there is a bag In with closure means II at one end, andprovided with gussets i2, an inturned valve I3, and a valve sleeve Id.The bag is shown as having two layers l5 of pa per and an inner layer [6of thermoplastic material of a heat-sealing nature, preferably havingappreciable elasticity. The material sold by the Goodrich Company underthe trade name of Koroseal has been employed successfully.

A reinforcing tape I1 is applied over the top of the bag and is sewed tothe bag, and may be adhered also. As shown in Fig. 2, the bag end isclosed by' a sewed seam I8 which passes through the bag walls andthereinforcing tape.

.The layer It is heat-sealed along the line of the closure. In thedrawings, this sealing is indicated at l9, just below the line ofstitches. The

sealing may extend along the line of stitches, but preferably shouldextend somewhat below also. toprevent the contents of the bag fromreaching the needle holes, even if those holes are sealed.

Any suitable heat-sealing layer it may be employed, andthe sealing maybe done before, after. or simultaneously with the sewing, althoughsealing prior to sewing and prior to the application of the reinforcingtape has some advantages. The Koroseal, mentioned above, may be pressedin liquid form onto a sheet of paper, so as'to form a lining adhered tothe paper, but is a material which maybe reheated to a point where twolayers thereof will coalesce without adhering to an ordinary papersurface, which fact is utilized in the manufacture of a sleeved valvebag.

' In the form of valve shown in Fig. 3, the inturned bag walls at I!have their sealing layer It on their side toward the unturned bag walls.but the edges of a sleeve ll are inserted as at 22 between the inneredges of the valve and the unturned bag wall. The sleeve consists of aninner layer of paper 20 having a sealing layer 2| applied thereto. Itwill be seen that where the edge of the sleeve is turned over at 22, thepaper layer is next to the unturned wall and will; not adhere theretowhen heat is applied to coalesce layer 2| with layer it at the inner endof the valve, as indicated at 23 in Fig. 3.

Preferably, the outer end of the sleeve is folded in at 24 so layers2l-.contact and maybe heat sealed at 25 after the bag has been filled.In forming the sleeve, a sheet may be used like that shown in Figs. 4and 5. This sheet may be folded along longitudinal line. 28, andtheninserted in the bag. The sheet is shown notched at its corners toprovide an outer flap 21, and inner flap 28 and side flaps 29. Flaps 21and 29 are first folded to bring their paper sides against the paper ofthe main sheet, while flap 28 is folded in the opposite direction, asshown in Fig. 5.

Then the sheet is folded about line 26, and the" flap 28 inserted at 22between" the inner end of the valve and the bag walls, as previously.described. The two flaps 29 are then at the upper edge of the sleeve,with their heat-sealing surfacesin contact. The bag at this stage may beheat-sealed as indicatedin Figs. 6 and '7.

Clamp members 30 may be op rated by lugs 3| in any convenient manner toclamp the end of the bag between them. The clamps extend alone theentire length of the seam, and are shaped to fit the bag end. providingfor greaterthickness at the gussets and reduced thickness along the topof the sleeve. A downwardlyeatending proaccuse jection 32 is provided atthe inner end of the sleeve and valve. Suitable conductors 33 areprovided, properly insulated by members 34 from the clamps, andconnected by means not shown to any suitable source of highfrequencyalternatin current. By this means, sufllcient heat is generatedto seal together layers l6 along line i9, including the ends of thegussets, and where there is a sleeve valve, layer 2! is simultaneouslysealed to layer It at the inner end of the valve and fiaps 29 are sealedtogether along the top of the sleeve.

After the bag end has been sealed in this way, a seam as at l8 may besewed along the end. Also, as previously indicated, the heat-sealingmight take lace after or simultaneously with the sewing. If preferred,the heat-sealing might be accomplished by applying heat by electrical orother means progressively across the bag end,

and while for convenience the description has described the operation astaking place at the upper end of the bag, in practice it is immaterialwhat position the bag is in during the sealing operation. Omission ofthe valve, and/or the gussets, merely simplifies the sealing operation,which may be otherwise the same as described above.

After the bag has been filled, the outer end of the sleeve may be sealedby applying heat so as to make the cpntacting surfaces of flaps 21coalesce, thereby completing the sealing of the bag and rendering itwaterand airtight. If the bag is to be used for chemical or othermaterial, the lining material is selected so as to retain the contentswithout injury to the bag.

Where the bag is closed by a sewed seam, it will be understood that thethread holds the bag walls together. If the inner surfaces coalescebelow the seam, there is a tendency for the contents to force thesesurfaces apart. Where the heat-sealing material is elastic, it stretchesenough to put the stress on the thread without forming a leakageopening. Less elasticity is required where the coalescence is directlyalong the line of stitches, especially where dependence is laced uponthe material filling the needle holes.

For some purposes, the bag and could be sufficiently sealed by employinga reinforcing tape with heat-sealing materialbetween the tape and thebag. The heat-sealing may be employed with bags which are left entirelyopen at the top until filled, or those which are only partly closed atthe filling end before filling.

While other heating means might result in sealing the bags, the highfrequency electric current is especially suitable for the purpose, sinceit makes possible a very rapid heating of the heat-sealing materialwithout injury .to paper outside thereof, and makes possible theapplication of the principle to a multiply bag and to the seam where thebag is gusset folded and so comprises many thicknesses of paper throughwhich heat would be conducted very slowly from ordinary externalapplication.

Where the thickness of the bag walls varies widely, suitable variationsmaybe made in the insulation between the conductor and the bag wall, asindicated in Fig. 8, or variations may be made in the frequency orvoltage of the current, so that the sealing will be accomplished in thesame time at all points across the bag, or if preferred, the current maybe applied for different intervals at different portions.

While for'simplicity acomplete lining of ther- 4 moplastic material hasbeen described, it will be readily understood that the material need bethermoplastic only where it is to be sealed, and any suitable liningmaterial may be employed at other points.

the valve formed of a sheet of paper having its outer side covered withthermoplastic material, its inner end folded outward and thethermoplastic material thereon being heat-sealed to the ba liningmaterial on the inner end of the valve, the longitudinal edges of thesheet being folded inward and their thermoplastic coatings beingheatsealed together along the line of said seam and the lining of saidbag being heat-sealed the rest of the way along said seam, and the outerend of the sleeve being inturned whereby it may be heat-sealed after thebag has been filled.

2. A plural ply bag comprising an inner ply of pliable plastic material,a surrounding ply of. paper, closure means for an end of the bag con- 1structecl and arranged 'with a valve at one corner, such valve having aninturned flap formed of said plies, and a valve sleeve therein whichincludes an inner ply of paper and an outer ply of pliable plasticmaterial, the plastic material of the bag inner ply and of said sleevebeing of a type such that contacting layers thereof will coalesce uponheating, surfaces ofthe plastic material along the inner edges of saidfiap being brought into contact and heat-sealed with respect to plasticsurfaces along the inner end edges of said sleeve, while leaving afilling opening through the sleeve to the exterior of the bag, and theouter end edges of the sleeve being turned inwardly, thus positioningplastic surfaces thereon for contact and heat-sealing of the outer endof the sleeve after the bag is filled.

3. A plural ply paper bag having an initially flattened tubular bodyportion with end closure means constructed and arranged with a valveatone corner of the bag, the portions of the bag at the region of said endclosure at least, having an inner ply of pliable plastic material, saidvalve having an inturned fiap formed of said plies, and a valve sleevetherein also initially flattened within the bag, said sleeve including3, ply of paper having at least on its inner end portions an outer plyof pliable plastic material, said plies of plastic material being of atype which will coalesce upon heating when in contact with each otherbut will not adhere effectively to paper, the inner end edges of saidsleeve being folded over to form a cufi-like portion embracing the inneredges of said fiap, and the surfaces of the plastic material along theinner edges of said flap being heat sealed with respect to plasticsurfaces along the foldedover edges of said sleeve, while leaving afilling opening through the sleeve to the exterior of the bag, the valveflap and sleeve therein being left free to be generally flattened upagainst the inside of the closure when the bag is expanded and filled.

4. A plural ply paper bag having a sewn seam end closure meansconstructed and arranged with a valve at one corner of the bag and theportions of the bag at the region of said end closure at least, havingan inner ply of pliable plastic material, said valve having an inturnedflap formed of said plies, and a valve sleeve therein which includes aninner ply of paper and an outer ply of pliable plastic material, saidplies of plastic material being of a type which will coalesce uponheating when in contact with each other but will not adhere efiectivelyto paper, the longitudinal edges of the plastic plies forming saidsleeve being folded inwardly of the sleeve and coalesced along a line ofjuncture to form the sleeve as a tube open at both ends, the opposedinner ply surfaces of the bag being heat sealed together along saidclosure means, and'the inner end edges oi said sleeve being folded overto form a cuff-like portion embracing the inner edges of said flap, andthe surfaces of the plastic material along the inner edges of said flapbeing heat sealed with respect to plastic surfaces along the folded-overedges of said sleeve, while leaving a filling opening through the'sleeveto the exterior of the bag, the valve flap and sleeve therein being leftfree to be generally flattened up against; the inside of the closurewhen the bag is expanded and

